If it's only for a 6x4 with a couple of ATVs then a Golf Tdi will handle it fine.
We have actually towed a couple of cars with the wife's 1.9 diesel, no problems at all - Unbraked trailer, GVM under 750kg of course
You just need to be aware of the downwards load limits on most new cars as they are quite light, although with a properly loaded 750kg trailer you should only have 10% down load i.e. 75kg